This invention relates generally to treatment of surimi, and particularly to a process to impart gel characteristics to surimi. There is a considerable interest in the possible utilization of fish infected with myxosporidian parasites such as Pacific whiting, Merluccius products, and Peruvian hake, Merluccius gayi, as a raw material for frozen surimi and surimi based products. These hakes are commonly found to be infected with myxosporidian parasites. The parasite myxosporidian is killed during the cooking process, but as this infection leads to protease-induced textural changes in cooked hake products, and to lowered surimi gel forming capacity, utilization of these hake for frozen surimi and surimi based products has been inhibited.
In order to improve the poor gel forming capacity of the infected hake, many attempts to apply protease inhibitors have been carried out. In the first step of frozen surimi manufacture, minced fish (mechanically separated fish meat) is washed with cold water, repeatedly. After being dewatered, the washed meat is mixed with cryoprotectants such as sugars and polyphosphates, and frozen. Surimi bases products are prepared by cooking surimi batter prepared from frozen surimi or the washed meat, ground with salt and other ingredients. According to the study of H. Groninger and his colleagues (Proceeding of International Symposium on Engineered Sea foods including Surimi, P. 199, National Fisheries Institute, 1985), a significant amount of protease remained in a Pacific whiting surimi sample prepared by the traditional method. Such trials involving washing treatment of minced meat with water containing protease inhibitors were not successful.
Early studies showed that the direct addition of more than 3% dried egg white, together with oxidants such as 500 ppm potassium bromate, to the washed meat was effective in improving the poor gel forming capacity of the infected hake. However, dried egg white alone is not sufficient to prepare a frozen surimi with high functionality. Also, the application of potassium bromate, the most effective oxidant, to frozen surimi and surimi based products is not permitted according to the Food Hygenetic Laws in Japan as well as in other countries. Therefore, in order to prepare frozen surimi and surimi based products with high functionality from myxosporidian infected fish, development of new ingredients having protease inhibiting activity is required.